1. Field of the Invention
The field of this invention relates to demetallization of metal contaminated catalysts. More particularly, this invention relates to a high pressure aqueous phase oxidation process to aid removal of metal contaminants from hydrocarbon conversion catalysts.
2. Prior Art
That conversion catalysts become contaminated or poisoned by absorbing or otherwise reacting with metals within a hydrocarbon feed is generally recognized. In order to maintain or recover catalytic activity of a catalyst the affect of metal poisons must be lessened, e.g. by removal of such metals from the catalyst. It is important that during the removal process of these metals that the catalyst itself not be adversely effected.
Erickson, U.S. Pat. No. 3,122,497 (1964) discloses the removal of metal contaminants from a cracking catalyst by the process of regenerating an aged catalyst, sulfiding the regenerated catalyst, and oxidizing to form water dispersible metal salts. Some of the oxidation methods disclosed are gas phase oxidations employing gaseous oxygen or mixtures of gaseous oxygen with inert gases such as nitrogen at temperatures from room temperature to 1300.degree. F. (704.degree. C.). Liquid phase oxidation employing dilute hydrogen peroxide or hypochlorous acid water solutions are also disclosed.
J. P. Connor, Jr. et al U.S. Pat. No. 3,123,548 (1964) discloses a method comprising separating a cracking catalyst from a hydrocracking reaction zone, contacting at a temperature from about 900.degree. F. to 1000.degree. F. (480.degree. C. to 538.degree. C.) the catalyst with molecular oxygen in a temperature range of from about 350.degree. to 1100.degree. F. (177.degree. to 593.degree. C.) for at least thirty minutes, contacting the oxygen-treated catalyst with a cation exchange resin in an aqueous medium at a selected pH so as to remove the metal contaminants and returning the catalyst to the hydrocracking reaction zone. The pH control of the medium in which a cation resin is employed is important to the efficiency of the removal of metal poisons within the catalyst.
Erickson et al. U.S. Pat. No. 3,147,209 (1964) discloses a method for demetalizing a silica-based cracking catalyst by a process comprising regenerating an aged catalyst to remove carbonaceous deposits, sulfiding the regenerated catalyst, contacting the sulfided catalyst at moderately elevated temperatures with an oxygen-containing gas-steam mixture to convert the metal sulfides to sulfates or other water-soluble or dispersible materials which are subsequently removed in a washing operation employing an aqueous medium. The sulfided catalyst is oxidized with a mixture of steam and molecular oxygen-containing gas at a temperature in the range 200.degree. to 1150.degree. F. (93.degree. to 621.degree. C.).
Schwartz U.S. Pat. No. 3,148,155 (1964) discloses an aqueous reductive wash of a regenerated, aged catalyst to remove metal contaminants such as nickel, vanadium and/or copper.
Anderson, U.S. Pat. No. 3,150,103 (1964) discloses an aqueous phase oxidation of a slurry comprising a sulfided and regenerated catalyst. The aqueous phase is disclosed to contain optionally ethylenediamine tetraacetic acid and ammonium hydroxide.
An aqueous phase oxidation of a sulfided catalyst which had previously been regenerated by means of an oxidative burn-off are disclosed in the following U.S. Patents expressly incorporated herein by reference: U.S. Pat. Nos. 2,764,557 (1956), 3,122,497 (1964), 3,146,188 (1964), 3,150,103 (1964), 3,150,072 (1964), 3,168,462 (1965), 3,182,011 (1965), 3,201,341 (1965), 3,216,951 (1965), 3,222,293 (1965), 3,252,918 (1966), 3,255,102 (1966), 3,379,639 (1968), 4,101,444 (1978) and 4,102,811 (1978). The use of aerated aqueous phase solutions which optionally are either acidic or contain a chelating agent are disclosed. However, the criticality of the partial pressure of oxygen is not recognized and is expressly taught away from. There is an express teaching that although higher oxidative partial pressures in an aqueous phase arising at temperatures much above 212.degree. F. (100.degree. C.) can be used, the benefits from using such higher partial pressures is alleged not to exist and the apparatus costs necessary to be able to utilize such higher oxidative partial pressures is alleged to be neither necessary nor desirable.
Specifically, all of the above-cited patents disclosing aqueous phase oxidation of a sulfided catalyst contain statements to the effect that the use of superatmospheric pressures have been allegedly found not to be necessary in order to perform the oxidation. Accordingly, none of the references suggest or teach the surprising benefits and advantages available when practicing the invention disclosed in this specification.
Aqueous phase oxidation employing peroxide is well known and expressly cited in several U.S. patents some of which have already been cited: U.S. Pat. Nos. 4,102,811 (1978), 4,101,444 (1978), 3,562,150 (1971) (not previously cited), 3,379,639 (1968), 3,255,102 (1966), 3,252,918 (1966), 3,201,341 (1965), 3,182,011 (1965), 3,168,462 (1965), 3,146,188 (1964) and 3,122,497 (1964).